Piston sand core



F. JARDINE PISTON SAND CORE Filed April 10, 1930 2 Sheets-s 1 & wk

F. JARDINE June 11, 1935.

no F/cA/w Milka/me Q YM attorney Patented June 11, 1935 Parana" mm2,004,661 PISTON SAND CORE I Frank Jardine, Cleveland,

- Aluminum Company of America,

Ohio, assignor to Pittsburgh,

Pa., a corporation of Pennsylvania Application April 10, 1930, SerialNo. 443,081

4 Claims.

This invention relates to the art of casting pistons and is primarilyconcerned with the provision of certain novel mold and core apparatusfor casting pistons which preferably are of an 5 aluminum base alloy.

It is now well recognized in this art that when molten alloy comes intocontact with the metal of permanent 'molds the accompanying chillingeffects provide a highly improved product as compared with casting ina'sand mold. The chilling causes a finer grain structure and alsoimproved properties of toughness, hardness and tensile strength. Whileit is well known practice today to utilize permanent molds as noted, theuse of permanent core parts is not so widespread. This is because of thefact that pistons of certain design have an internal structure of suchintricacy that it is impossible to define the same with a permanentcore.

In view of the foregoing, this invention contemplates the provision of acore assembly, which comprises, for the major part, a permanent coreconstruction, together with non-permanent core parts which are designedto core out inaccessible recesses in the piston. The invention alsocomprehends an arrangement wherein the non-permanent core parts aresupported and carried by the permanent core construction.

More in detail, the invention has in view the provision of a coreassembly including sand cores which are carried by metal supportingmembers embedded therein. The latter are detachably anchored in thepermanent core construction and are so designed as not to prevent theremoval of the latter from the piston after casting.

These and other more detailed objects and advantages will becomeapparent as the description of the invention proceeds. For a full andmore complete understanding thereof, reference may be had to thefollowing description and accompanying drawings, wherein:

Figure l is a vertical section, somewhat fragmentary, through moldingapparatus designed in accordance with this invention.

Figure 2 is a section taken on the line 2-2 of Figure 3.

Figure 3 is a horizontal section taken about on the plane indicated bythe line 33 of Figure 2.

Figure 4 is a detached elevational showing of iii one of the sand coreparts,

Figure 5 is a bottom plan view of the core part shown in Figure 4.

Figure 6 is a horizontal section taken on line 6-6 of Figure 2, omittingthe metal of the piston;

' bosses.

Figure 7 is a showing similar to Figure 6 taken on line 1-1 of Figure 2;

Figure 8 is a showing similar to Figure 6 taken on line 8-8 of Figure 2;and

Figure 9 is a perspective view of the permanent 5 and sand cores asassembled within the mold.

Referring now to the drawings, a permanent mold of any conventional typeis represented by the reference character A. This mold serves to definethe outer contour of the piston, which is cast therein. In the presentinstance the piston B is shown as including certain internalconstruction comprising wrist pin bosses l and hangers 2 connecting thebosses with top 3 of the piston. Obviously, the wrist pin bosses,together 15 with the hangers 2, wall 4, and top I, define recesseswhich'are inaccessible to a permanent core as the latter could not bewithdrawn therefrom after casting. These recesses are referred to as R.g The remainder of the internal structure of the piston is susceptibleto formation by a permanent core which is shown at C. The latter may beof a sectional construction to facilitate removal after casting or asshown in Figure 3, of a single piece, but its design is not material tothis inventon other than that it be formed with vertically extendingrecesses 5.

In the casting of the piston, recesses R are formed by properly shapednon-permanent cores 6 of sand. Partially embedded in'the latter, withportions projecting therefrom, are wire inserts I. The latter are bentover at 8 to provide a firm support for the core. The downwardlyprojecting portions of the inserts 1 are fitted in the 35 recesses 5 andare preferably deformed at 9 to provide for a good frictional engagementwith the permanent core 0. In the embodiment illustrated each sand corepart 6 is shown as provided with two of the inserts 1, each of which islocated in a recess 5 adjacent to one of the wrist pin Obviously, thenumber of inserts employed can be varied with the size and shape ofthepiston cast.

The permanent core and sand cores when positioned in the mold arearranged as shown in Figure 9. The vertical hanger 2 being formed withinthe void 2' and the strut I 1 formed in the void H. The hanger 2 and thestruts I! are joined to 'each other through the medium of the, pinbosses as shown" in Figure 7. As best shown in Figure 7 the sand core 6curves toward the permanent core C to form the void for strut IT. Thesurface of the sand core adjacent the mold at this curved tip forms theinner surface 65 v of the piston skirt. The surface of the sand coreadjacent the permanent core formsthe outer surface of the strut II. Thusthe sand cores 6 form a recess that ism-entrant towards the pin bossesin order to form curved struts. It would be obviously impossible towithdraw the perma nent core from the mold should the permanent core beutilized for forming the upper edge of the curved struts. The lower edgeof the curved struts is formed in a groove of the permanent core asshown in Figures 9 and 8. The groove is curved as the sand core inFigure 7 and the two curves are complementary to form the voids H.

In carrying out a casting operation in accordance with this inventionthe sand cores 6 are first properly built up on the wire inserts 1. Thepermanent core construction C is then assembled and the sand core parts6 attached thereto by inserting the members I in the recesses .5. Theentire core assembly is then inserted in the mold A and the moltenaluminum alloy poured. After freezing of the piston, the permanent coreis withdrawn from the interior of the piston and the mold A is removedfrom about the piston. In removing the permanent core C, the wireinserts 1 will pull out of the recesses 5 as they are still held in thesand cores 6. The sand core parts 6 may now be broken up and punched outin the usual manner. The inserts are removed as the sand core breaks up.

While a preferred specific embodiment of the invention is herein setforth, it is to be understood that I am not to be limited to the exactconstructions illustrated and described because various modificationsmight be made in putting the invention into practice within the purviewof the appended claims.

What I claim is:

1. Molding apparatus comprising a, permanent mold having a castingcavity therein shaped to form the outer walls of a piston, a permanentcore construction removably positioned within said casting cavity andspaced from .the walls thereof to define the inner surfaces of thepiston skirt at the open end thereof, the sides of said coreconstruction being offset inwardly to form the inner surfaces of a pairof piston pin bosses and the inner surfaces of webs extending from saidpiston pin bosses to the skirt, the offset portion of said coreconstruction being extended to form a portion of the inner surface ofthe piston head and to form the inner walls of a pair of hangersextending from said piston pin bosses to the head and a pair of sandcores arranged to provide re-entrant recesses between each of the sandcores and the permanent core to form.the outer side surfaces of thehangers and the webs and the adjacent inner surfaces of the piston skirtand head.

2. Molding apparatus comprising a permanent mold having a casting cavitytherein shaped to form the outer walls of a piston, a permanent coreconstruction removably positioned within .-said casting cavity andspaced from the walls thereof to define the inner surfaces of the pistonskirt at the open end thereof, the sides of said core construction beingoffset inwardly to form the inner surfaces of a pair of piston pinbosses and the inner surfaces of webs extending from said piston pinbosses to the skirt, the offset portion of said core construction beingextended to form a portion of the inner surface of the piston head andto form the inner walls of a pair of hangers extending from said pistonpin bosses to the head' and a pair of sand cores arranged to providere-entrant recesses between each sand core and the permanent core so asto form the outer side surfaces of the hangers and the webs and theadjacent inner surfaces of the piston skirt and head, said sand coresbeing supported by said permanentcore construction.

3. In apparatus for molding pistons or the like, an outer mold, apermanent core removably extending into the outer mold, additionalpermanent coring means removably extending thru substantially oppositesides of the outer mold and against the first named core, a pair ofnonpermanent cores supported by the first named core, and wirestraddling the second-named coring means releasably connecting saidnon-permanent cores to the first named core.

4. In apparatus for molding pistons or the like, an outer mold, apermanent core removably extending into the outer mold, additionalpermanent coring means extending through opposite sides of the outermold and against said first named core, a, pair of non-permanent corespositioned on opposite sides of said first'named core and spacedtherefrom and from said outer mold to provide casting cavities, saidnon-permanent cores being spaced from said additional permanent coringmeans and substantially straddling the same, and wire retainer membersimbedded in said non-permanent cores, said first named core being formedwith longitudinally openings receiving and frictionally retaining saidretainer members.

FRANK JARDINE.

